In a veneer handling apparatus having a clipper for continuously cutting a ribbon of veneer into sheets, e.g. cut sheets each having a format size of predetermined lengthwise and widthwise dimensions, and also a stacker for stacking such cut sheets into a pile at the final station thereof, it is desirable that the cut sheets adjacent to one another should be fed to the stacker with sufficient space therebetween to ensure smoothness in the stacking operation without causing harmful veneer jamming at the stacker. A short period of time is usually required for each sheet to be positioned properly with respect to a stacker stand on which it is to be stacked and then to be dropped onto a previously formed pile of sheets. If adjacent sheets are fed with insufficient space, a succeeding sheet will enter into the stacker before its preceding sheet is properly dropped for stacking, thus inviting trouble such as interference or jamming of such veneer sheets at the stacking station.
For providing a space between adjacent cut sheets necessary for the above smoothness in stacking operation, there has been proposed a veneer handling apparatus which includes two layers of conveyors arranged one above the other and adapted to receive alternately one incoming sheet at a time. In this proposed apparatus according to the prior art, the upper conveyor has a greater length than the lower one and the two conveyors are arranged so as to meet or converge at a downstream point so that a preceding sheet which moves on the upper conveyor for a greater distance may be placed at the converging point over its succeeding sheet which comes out from the lower conveyor. A pair of these sheets is further moved in such combined relation toward the stacker with a sufficient space formed with respect to their adjacent succeeding pair of similarly combined sheets. In this apparatus, the upper conveyor has a length greater than that of the lower conveyor, as measured from the upstream end thereof to their meeting point, the difference between these lengths being substantially an odd number, e.g. 1, 3 and so forth, times the dimension of the sheet between its opposite cut ends, or the dimension thereof along which it is advanced on the conveyor.
For better understanding of major object that the present invention intends to achieve, the operation of the above prior art will be described more in detail with reference to the illustrative diagrams shown in FIGS. 3A to 3G, wherein the upper conveyor 40 has a distance three times the dimension D of cut sheets each designated by the letter S followed by numerals of serial numbers, and the lower conveyor 41 has a distance two times the dimension D, thus the difference in length being one time the dimension D of the sheet. It is to be understood that for the sake of distinguishing of cut veneer sheets a little space is shown between two adjacent sheets on the upstream or left-hand side of the conveyors 40, 41. The space formed in actual veneer handling practice is only of a magnitude that substantially corresponds to a cutting line between two veneer sheets. Now supposing that successively fed veneer sheets, e.g. S1 through S5, are all sound or have therein no defect, the first sheet S1 fed to the upper conveyor 40 will have to travel a greater distance than its succeeding sheet S2 moving on the lower conveyor 41 by a distance substantially equal to the dimension D of the sheets. Therefore, these two sheets S1 and S2 will meet at the converging point of the two conveyors, as shown in FIG. 3C, and come out therefrom with the sheet S1 placed over the sheet S2 to be advanced further toward a stacker (not shown). Similarly, the sheet S3 travelling on the upper conveyor 40 will be put over the sheet S4 then coming out from the lower conveyor 41. As shown in FIG. 3D, a space substantially equal to the dimension d can be formed between the two adjacent pairs of combined sheets.
However, this conventional apparatus will not perform its intended function if a defective veneer sheet, e.g. sheet S6, is found and therefore removed from the production line, as indicated by the dashed line in FIG. 3D. In such a case, when the sheet S5 reaches the downstream end of the upper conveyor 40, the succeeding sheet S7 is moving on the lower conveyor 41 behind the sheet S5 by a distance of the dimension D, as seen in the step of FIG. 3A. Therefore, the sheet S7 will come out from the conveyor 41 just behind its preceding sheet S5 with very little space formed therebetween, thereby making it difficult to stack these two sheets properly at the subsequent stacking station of the apparatus. The result will be that veneer jamming will result.
In this way, the above-described prior art can function properly when stacking all cut sheets including defective ones, but encounters a problem when such defective sheets are to be removed from the working line of the apparatus.